MSC cruises are great for families and have a lot to do, i personally went on the msc Splendida, its a perfectly sized boat with loads of stuff on board, 4 swimming pools, an exercise room, squash court, the chance to simulate the thrill of Formula 1 and loads more, the kids area is really cool, its like a artic room full of penguins and things.
***Edited to remove commercial reference***